1. Field of the Invention
The present invention generally concerns fulgides, photochromism, and fluorescing photochromes.
The present invention particularly concerns stable fluorescing photochromic fulgides.
2. Description of the Prior Art
Photochromic fulgides, a class of organic compounds which are capable reversible light-induced coloration, were discovered by Stobbe and then further developed by several research groups. See Stobbe, Berichte, 40, 3372 (1907).
Photochromic fulgides exhibit several important physical properties, such as thermal stability of both colorless and colored forms, high photoreaction efficiency, high fatigue resistance to repeated coloration-bleaching cycles and light power. Photochromic fulgides are promising candidates for many technological applications including use in recording media, particularly in erasable optical memory devices. See D. A. Parthenopoulos and P. M. Rentzepis, Journal of Molecular Structure, 224,297 (1990).
For their utilization as 3D optical memory device materialsxe2x80x94where the accessing of information is achieved by means of the fluorescence emitted by the written bitsxe2x80x94the colored form of the photochromic material will desirably fluoresce when illuminated with light. See A. S. Dvornikov, S. Esener and P. M. Rentzepis, in J. Jahns and S. H. Lee (Eds.), Optical 5. Computing Hardware, Academic Press Inc., 1993, pp. 287-325. See also A. S. Dvornikov and P. M. Rentzepis, in R. A. Lessard and W. F. Frank (Eds.), Polymer in optics: physics, chemistry and applications, Critical reviews of optical science and technology, v. CR63, SPIE, 1996, pp. 239-261.
Recently, a series of heteroclic photochromic fulgides have been synthesized. See H. G. Heller and J. R. Langan, J. Chem. Soc. Perkin Trans. 2, 341 (1981); E A. Kaneko, A. Tomoda, M. Ishizuka, H. Suzuki, and Ryoka Matsushima, Bull. Chem. Soc. Jpn. 61, 3569 (1988); and H. G. Reller and S. Oliver, Chem. Soc. Perkin Trans. 1, 197 (1981).
These heteroclic photochromic fulgides are thermally stable, fatigue-resistant and undergo near-quantitative conversion to their colored forms upon exposure to UV light. However, these photochromic fulgides do not fluorescein either their colored or their colorless form. See A. S. Dvornikov and P. M. Rentzepis, in R. A. Lessard and W. F. Frank (Eds.), Poiymer in optics: phtysics, chemistry and applications, Critical reviews of optical science and technology, v. CR63, SPIE, 1996, pp. 239-261, op. cit.
To the best knowledge of the inventors no data has been published on any fluorescing fulgides. The synthesis and photochromic properties of some 2-indolyfulgides have been reported. See I. Y. Grishin, Y. M. Chunaev, N. M. Przhiyalgovskaya, and A. V. Metelit, Khim. Geterotsikl. Soedin, 3, 422 (1992); and I. Y. Grishin, N. M. Przhiyalgovskaya, Y. M. Chunaev. V. F Mandzhikov, L. N. Kurkovskaya, and N. N. Suvorov, Khim. Geterotsikl. Soedin., 7, 907 (1989).
The present invention contemplates photochromic fulgides that are fluorescing or, more exactly, that can be induced to fluoresce by radiation of an appropriate frequency. The fluorescent photochromic fulgides of the present invention are particularly suitable for optical memories.
The fluorescent photochromic fulgides of the present invention exhibit all the important physical properties of photochromic fulgides; to wit: thermal stability of both colorless and colored forms, high photoreaction efficiency, high fatigue resistance to they repeated coloration-bleaching cycles and light power. Moreover, they are strongly fluorescent in one (only) stable form.
In one of its aspects the present invention is embodied in a photochromic chemical consisting essentially of colored fluorescent heterocyclic fulgides.
In another of its aspects the present invention is embodied in heterocyclic photochromic fulgides Consisting essentially of colored 2-indolyfulgides capable of excitation by at least ultraviolet light to fluoresce.
These heterocyclic photochromic fulgides are preferably synthesized by process of (1) condensation of 1,3-dimethyl-(5-substituted) indole -2-carboxaldehyde, with diethyl iospropylidenesuccinate as a key intermediate; followed by (2) hydrolysis; and (3) intramolecular acid anhydride formation.
In yet another of its aspects the present invention is embodied in a family of molecules of the form shown in FIG. 2 where attached radical R is drawn from the group R=H; R=OCH3; R=CH3; R=Cl; and R=F.
These and other aspects and attributes of the present invention will become increasingly clear upon reference to the following drawings and accompanying specification.